In the instance of users creating Multiple Accounts, there are at least two motivating reasons. (1): The user has lost access to their account through some means of website or human error; (2): forgotten their password and cannot access it with a new password; (3): the user in question is a returning vandal and the account in question is that of a Sock Puppet Account.
Here at the Sailor Moon Dub Wiki, the policy is that the latter is absolutely unacceptable. We won't block you if you have forgotten your password. However, it is your responsibility to let the admins know that you've encountered issues with your account so the proper actions can be taken. But, if you're a vandal and create a new account, you and your other account will be blocked, with the new one infinitely.
If you have forgotten your password, you can create a new account but notify an administrator. They will have to block your old account infinitely and add on the user page that you have a new account, or just delete the old account. You can no longer use that account, even if you remember the password.
Abusing Multiple Accounts
If you are a vandal and create a new account, you will be blocked for a length of time as well as this other account being blocked infinitely. Even if you do not vandalize using it, the potential to do so is there. Just sit out your block and wait. Then try to be a good person and do not vandalize any more and actually help.